It's a bitch to fly low over terrain on an airless world.
The rules are the same for Luna and the Galileans.There's no
lift, so you constantly have to fire the ventral thrusters to keep from skidding
into the ground.Thrusters to keep you level; main drive to
keep you moving.If you were to just tilt up with the main
drive, you don't stay low for very long.Plus you can't see
where you're going.It's okay for flat terrain, but useless
for badlands.

Now some booksmart kid is bound to point out that you can get to
orbit with the energy you waste hovering for just twenty minutes.True enough.And you'll need twice that to get you
back to zero velocity.And yes, with 2kps of delta-v you
could also hop a parabola to the far side of the world.But
that doesn't keep you low to the ground, either.

Now sure, you could theoretically fly an orbit just a few dozen meters off
the ground, but that nasty terrain will kill you.Not even a
machine can react fast enough to something unexpected when you're flying at
2,000 meters per second.Better to go slow, no more than a
third of that if you're really good, a tenth if you're safe.
It wastes fuel, but it keeps you from getting dead.